This invention relates to a new and improved dental laboratory die tray, and in particular to a die tray especially suited for use in handling the refractory materials now being used in the production of dental prosthesis.
When a patient in need of crown and/or bridge dental restorative work visits a dentist, the dentist carves the affected tooth or teeth into an appropriate preparation and takes an impression of the patient's mouth. This impression is sent to a dental laboratory, along with a prescription for the dental prosthesis to be made.
Using a single pour technique the technician is able to pour the impression and the base with one mix by mixing the die stone and pouring into both the base and the impression, slightly over filling each. The technician should quickly invert the impression and position it on the filled tray. When the die stone sets, any overflow can be trimmed. The die tray allows the technician to remove the working model from the tray, separate the individual tooth or teeth to be worked on and return the working model (often in several pieces by this time) to the die tray, while maintaining the original registration of the individual teeth to the die tray and to each other.
A double pour technique can also be used in which the technician pours a working model of the patients teeth by filling the dentist's impression with die stone and allowing it to set. The portion of the model containing the affected tooth or teeth is then imbedded into a die tray filled with additional die stone.
The die tray also permits the working model to be mounted to a dental articulator. This enables the technician to develop the proper anatomy and functional occlusion of the prosthesis while still having the ability to remove the individual tooth die or dies for further work.
In the past, dental model systems were produced by plating copper or silver on the portion of the impression which was going to be restored. A cold cure acrylic resin was poured into the plated recesses and after setting, was removed and trimmed into a die. The acrylic die was re-inserted into the impression and held in position with wax. Die stone was poured into the impression, covering the die, and creating a model with a removable die.
An alternate method of making a removable die system consisted of pouring dental die stone into the impression sufficient to reproduce the tooth anatomy, grinding a flat base on the model, and drilling die pin holes into the individual teeth which are to become dies. Die pins are placed into the die stone of the teeth to be restored, and the bases of the teeth are coated with a release agent. A second pouring of a die stone encloses the pins and makes up the base of the model. The individual dies are cut from the model with a saw so that they can be removed, worked on and returned to their original position.
Because of the amount of labor involved in creating the acrylic die or the pin die system, an alternative was developed which used a die tray with an external registration to replace the die pin system. One type, sometimes called a die lock tray, has fixed sides and reinforcing ribs between the sides and an "L" shaped moveable clamp overlying a portion of the top of the tray, with a detachable hinge on one end. The moveable clamp can be removed, permitting the dies to be removed from the tray, worked on and returned to the tray without losing the original registration.
Other prior die tray systems, including one known as the Accu-Trac, consist of a tray containing an upward opening arch shaped, serrated grove to register the model, and hinged retainer clips to retain the model of the tray. The model cast and individual tooth dies are prepared in a manner similar to the methods previously described. This type of die tray positions the individual dies laterally by the upward opening groove, vertically by the retaining clips and mesially-distally by the serrated grooves.
Refractory materials are now used in the production of crowns and dentures and have been successful in producing artificial teeth with a porcelain finish of a luster and depth corresponding to that of natural teeth. While the die stone is very satisfactory in producing models from mouth impressions, the die stone has not been satisfactory in these new manufacturing processes due to the high processing temperatures involved. Therefore after the initial model is produced, a second model of a refractory material is needed for use in the high temperature casting and coating operations. The prior art die trays have not been satisfactory for these operations, and it is an object of the present invention to provide a new and improved dental laboratory die tray suitable for producing models and working on models, especially for higher operating temperatures. These and other objects, advantages, features and results will more fully appear in the course of the following description.